Changing period and phase of alternating currents



No. 6l5,954. Patented Dec. l3,.|898. c. s. BRADLEY.

CHANGING PERIOD AND PHASE 0F ALTEBNATING CURRENTS.

(Application filed June 22, 1896. Renewed No 17. 1898.)

(No Model.)

WITNESSES: JNVENTOR A; ATTORNEY UNITED STATES PATENT OFFICE.

CHARLES S. BRADLEY, OF AVON, NEYV YO RK, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF NEW YORK.

CHANGING PERIOD AND PHASE OF ALTERNATING CURRENTS.

SPECIFICATION forming part of Letters Patent no. 615,954, dated December 13, 1898.

Application filed June 22,1896. Renewed November 17, 1898x Serial No. 6963737. (No model.)

To all whom i may 'ww r may be taken. The motor-generator may be Be it known that 1, CHARLES S. BRADLEY, driven by asingle-phase current delivered to a citizen of the United States, and a resident its magnetizing-winding orbya polyphase curof Avon, in the county of Livingston and State rent delivered thereto.

of New York, have invented certain new and My invention therefore comprises a method useful Improvementsin Changing the Period of altering the time period of an alternating and Phase of Alternating Current-s, of which current consisting in charging one element the following is a specification. with an alternating current to charge the The object of this invention is to permit same magnetically and create a shifting magto the period or rate of an alternating current netic field and adjusting the circuits of a 00- or a plurality of such currents to be changed operating element movable with relation to and varied as desired for the operation of the other, so as to render them electrically motors and other translating devices and to consonous at the rate of alternation desired. permit a single alternating current, or more It comprises alsoalnotor-generator provided I 5 than one, to be converted into. any desired with a magnetizing-winding and a secondary number of phasially different currents. winding relatively movable thereto adjusted In carrying out the invention I operate a or capable of adjustment to produce electrical motor-generatortheprimarywinding of which consonance with the desired time period or is adapted, either alone or by the assistance rate of alternation.

20 of the armature reaction, to develop a rotary It comprises also such an organization promagnetic field and the secondary or generatvided with distributing connections to proing winding of which is connected in circuit duce any desired number of phases in a conwith devices for varying the capacity or insumption-circuit. An organization of this ductance, or both, to render said circuit conkind is especially advantageous in certain 25 sonous to adesired rate of alternation needed kinds of work-as, for example, in operating in a consumption or distribution circuit. I trains of cars, where a number of inductionhave described a motor operating under 0011- motors are simultaneously started and con trol of such adjusting devices in a patent trolled. It is desirable with such motors that granted to meApril 7, 1896, No. 557,957. The in starting up they should be supplied with 30 generating-winding of the motor-generator currents of slow rate or long period and that may generate any rate of alternation,dependas they gain in speed the rate should be quick ing on the capacity-inductance product of the ened. winding and its connected circuits. The 0011- In the accompanying drawing, which illusdition of adjustment is approximately detertrates, diagrammatically, myinvention, Aisa 5 mined bythe formula for electrical resonance motor-generator the primary element P of in which the capacity of the circuits multiwhich is provided with a winding connected plied by their inductance equals twenty-five with a supply-circuit 1 2 or 1 2 3. For conthousandthreehundred,dividedbythe square venience of explanation we will first assume of the rate of alternation. When such an adthat the winding is a closed coil tapped at 40 justmentis made fora desired rate of alternathree symmetrical points and connected with tion, the circuits arein electrical consonance, a triphase supply-circuit l 2 3. A rotary as fully set forth in my patent above referred magnetic field will under such conditions be to. In an organization of this kind the devices set up in the primary core. In inductive rewhich are provided for varying the capacitylation to the rotary field is a secondary or 5 inductance product are set for the period or generating element S, the winding of which 5 rate desired,and the motor-generatorwill then leads through brushes b b 17 into a circuit develop such rate. The generating-Winding including devices for varying the capacity may be opened or tapped at any desired numinductance product of the secondary wind- .ber of symmetrically-distributed points, and ing and its connected external circuit. These 50 from such points currents diifering in phase devices are preferably condensers c c c in zoo each branch of the polyphase circuit connecting with the brushes Z) K) b which are rendered adjustable by any suitable device for varying their surface. As shown, a comm 011 controlling-handle II may actuate a switchlever in each condenser branch and graduate by a single movement the capacity of all the condensers similarly. The inductance factor of the equation which determines consonance may, however, be varied instead of the capacity with similar results. As this matter of the interchangeability of condensers and inductance for this purpose was fully considered in my patent hereinbefore referred to it need not be further described here. In parallel arc with the condensers are distributing-mains a Z) c of a consumption-circuit supplying translating devices. Induction-motors are shown at M M, since the invention is especially applicable to their operation. Other devices may, however, be supplied, if desired. When the motor-generator is in operation, the secondary element follows the rotary field; but as its magnetization depends upon the slip between the movable and fixed elements of the generator the secondary currents generated will obviously be of slower rate than the primary currents. The rate is, however, dependent upon the capacity-inductance product of its circuits. If the condensers are adjusted for a low rate, the generator will assume a definite speed closely approximating this predetermined rate. Either the primary or the secondary element of the generator may be the movable member. If a sin gle-phase chargingcurrent be em ployed, as indicated in full lines, the reaction of the secondary member and the condensers will assist the single-phase current in developing a rotary field in the primary element P, and similar results to those hereinbefore described will ensue in the gen erating and consumption circuits. \Vith a single-phase system an auxiliary device for starting the motor-generator must be used. On starting up the motors the lowest rate in the circuit which supplies them is desirable, which will of course require the greatest oapacity-inductance product to produce electrical consonance. If capacity he the variable factor, the maximum amount of such capacity should be in circuit when the motors are starting. This condition of adjustment is shown in the drawing. This adjustment furnishes the greatest storage capacity just when it is needed to give torque to the motors. Moreover, as the revolving element of the motorgenerator is at such a time operating at a maximum speed, because the rate is lowest when the difference in speed of the two generator elements is least, great momentum is stored, which greatly adds to the starting efforts of the motors. As the motors rise in speed the condenser is reduced, slowing down the generator. The maximum capacity of the condensers should be of a value to produce consonance when all of the motors are starting and are at low speed. In shutting down the motors the condensers may be all cut in gradually, thereby destroying the consonous adjustment for the higher rate of alternation under which the motors were operating and reducing the torque, thus causing the motors to slow down. In controlling the speed of the motors the condenser-switch should be gradually shifted, thereby altering the capacity by degrees, and consequently altering the speed of the motor-generator and motors. If several cars are cut off and the number of supplied motors reduced, the inductance will be only fractiona-lly altered, since the motors are in multiple arc with the supply-circuit.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-=- 1. The method of altering the rate of an alternating current consisting in leading said current through a motor-generator, feeding a work-circuit from the secondary of said generator, and controlling the rate by altering the phase relation of the work-current.

2. The method of changing the rate of an alternating current, consisting in setting up a magnetic field by said current, and operating in inductive relation thereto a circuit rendered consonous to the desired rate.

3. The method of changing the rate of an alternating current, consisting in setting up a shifting magnetic field by said current, driving a motor element thereby, and adjust ing the capacity-inductance product of the secondary circuit for the desired rate.

at. The method of producing a variable rate from an alternating current of definite rate, consisting in operating an induction-motor generator thereby, and varying the capacityinductance product of the secondary circuit of the motor-generator.

5. The combination of a motor-generator comprising a primary winding, asecondary winding, condensers connected with said secondary winding, and translating devices sup plied by said secondary windin 6. A motor-generator provided with a fieldmaguet adapted to be charged by an alternating current, and an armature including a condenser in its circuit.

7. A motor-generator provided with a fieldmagnet adapted to be charged by an alternating current, and an armature including devices for varying the capacity-inductance product of its circuit.

8. A motor-generator provided with a field magnet adapted to be charged by an alternating current, and a polyphase armature having a condenser in each circuit.

9. A motor-generator provided with a field magnet adapted to be charged by an alternating current, and a polyphase armature having in each circuit devices for varying the capacity-inductance product.

Ice

thereby, a consumption-circuit, containing one or more induction-motors fed by the secondary of the mot0r-generator,and condensers 15 in said secondary circuit.

In testimony whereof I have hereunto subscribed my name this 23d day of May, A. D. 1896.

CHARLES S. BRADLEY.

Witnesses:

C. R. WATERBURY, ROBT. H. READ. 

